[leetcode]263. Ugly Number

题目

Write a program to check whether a given number is an ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 6, 8 are ugly while 14 is not ugly since it includes another prime factor 7.

Note that 1 is typically treated as an ugly number.

代码

1.

public  boolean isUgly(int num) {
		 if(num <= 0){ return false;}
		 if(num == 1 || num == 2 || num == 3 || num == 5){return true;}
		 while(num >= 2){
			 if(num % 2 !=0){
				 break;
			 }
			 else {
				 num = num /2;
			 }
		 }
		 if(num == 1){
			 return true;
		 }else{
			 while(num >= 3){
				 if(num % 3 !=0){
					 break;
				 }else{
					 num = num/3;
				 }
				 
			 }
			 if(num ==1){
				 return true;
			 }else{
				 while(num >=5){
					 if(num % 5 !=0){
						 break;
					 }else{
						 num = num/5;
					 }
				 }
			 }
			 if(num == 1){
				 return true;
			 }
			 
		 }
		 return false;
	 }

2.

public  boolean isUgly(int num) {
	      if(num <= 0){
	          return false;
	      }
	      if(num == 1){
	          return true;
	      }
	      if( num % 2 == 0 ){
	          return isUgly(num/2);
	      }
	      if(num % 3 == 0){
	          return isUgly(num/3);
	      }
	      if(num % 5 == 0){
	          return isUgly(num /5);
	      }
	      return false;
	        
	    }